WT1 gene (Wilms' tumor gene 1) has been identified as one of causative genes of Wilms' tumor that is a childhood renal tumor (Cell 60: 509, 1990, Nature 343: 774, 1990). WT1 gene encodes the transcription factor WT1, and WT1 plays an important role in many processes such as proliferation, differentiation and apoptosis of cells, and development of tissues (Int. Rev. Cytol. 181: 151, 1998). The WT1 gene was originally defined as a tumor suppressor gene. However, subsequent studies revealed that WT1 gene is expressed in leukemia and various solid cancers including lung cancer and breast cancer, indicating that WT 1 gene rather exerts an oncogenic function promoting cancer growth. In addition, it was demonstrated in vitro that, when peripheral blood mononuclear cells positive for HLA-A*0201 or HLA-A*2402 are stimulated with WT1-derived peptides, peptide-specific cytotoxic T-lymphocytes (CTLs) are induced and kill leukemia or solid tumor cells which endogenously express WT1. These results demonstrated that WT1 is a promising target molecule of cancer immunotherapy (Int. J. Hematol 76: 127, 2002). However, it has been neither elucidated whether said WT1 contains a peptide portion(s) capable of binding to HLA-A26 antigen nor reported that there is such a peptide(s).
In addition, although binding sequences for a cancer antigen peptide capable of binding to HLA-A*0201 (a member of HLA-A2 antigens) were deduced (WO 00/18795), only a few cancer antigen peptides have been proved to be effective so far (WO 00/06602 and WO 00/026249).